Geometric Measurements Research Articles

A new approach to measure fundamental microstructural influences on the magnetic properties of electrical steel using a miniaturized single sheet tester

Magnetic properties of electrical steel are usually measured on Single Sheet Testers, Epstein frames or ring cores. Due to the geometric dimensions and measurement principles of these standardized setups, the fundamental microstructural influences on the magnetic behavior, e.g., deformation structures, crystal orientation or grain boundaries, are difficult to separate and quantify. In this paper, a miniaturized Single Sheet Tester is presented that allows the characterization of industrial steel sheets as well as from in size limited single, bi- and oligocrystals starting from samples with dimensions of 10 × 22 mm. Thereby, the measurement of global magnetic properties is coupled with microstructural analysis methods to allow the investigation of micro scale magnetic effects. An effect of grain orientation, grain boundaries and deformation structures has already been identified with the presented experimental setup. In addition, a correction function is introduced to allow quantitative comparisons between differently sized Single Sheet Testers. This approach is not limited to the presented Single Sheet Tester geometry, but can also be used to compare the results of Single Sheet Testers of various sizes. The results of the miniaturized Single Sheet Tester were validated on five industrial electrical steel grades. Furthermore, first results of differently oriented single crystals as well as measurements on grain-oriented electrical steel are shown to prove the additional value of the miniaturized Single Sheet Tester geometry.

Post-fire cross-sectional behaviour of hot-rolled austenitic stainless steel channel section stub columns under combined compression and minor-axis bending

The present paper reports experimental and numerical investigations into the post-fire cross-sectional behaviour and residual resistances of hot-rolled austenitic stainless steel channel section stub columns under combined compression and minor-axis bending. An experimental programme included heating, soaking and cooling of specimens as well as post-fire initial local geometric imperfection measurements and minor-axis eccentric compression tests on fourteen specimens. The minor-axis eccentric compression test results were used in a parallel numerical modelling programme for validation of finite element models, which were then adopted to perform a series of parametric studies to generate further numerical data. Since there are no existing design rules for stainless steel structures after exposure to elevated temperatures, the relevant codified ambient temperature design interaction curves in combination with post-fire material properties were evaluated for their applicability to eccentrically loaded hot-rolled austenitic stainless steel channel section stub columns after exposure to elevated temperatures. The evaluation results revealed that the design interaction curves given in the European code and American specification led to rather conservative and scattered resistance predictions, which were attributed to the conservative end points and inefficient shapes. To address the shortcomings, new design interaction curves anchored to more accurate end points and having more efficient shapes were developed and resulted in more accurate and consistent resistance predictions than their codified counterparts. The reliability of the new design interaction curves was also confirmed by means of statistical analyses.

Cross-sectional behaviour of press-braked S690 high strength steel slender channel section stub columns under minor-axis combined loading

This paper reports laboratory testing and numerical modelling on the cross-sectional behaviour and resistances of press-braked S690 high strength steel slender channel section stub columns under combined compression and minor-axis bending. A testing programme, including initial geometric imperfection measurements and ten minor-axis eccentric compression tests, was firstly conducted. This was accompanied by a numerical modelling programme, including a validation study, where finite element models were developed and validated against test results, and a series of parametric studies, where the validated finite element models were used to generate further numerical data. The obtained test and numerical data were then adopted to evaluate the current codified design interaction curves for press-braked S690 high strength steel slender channel section stub columns under combined compression and minor-axis bending, as provided in the European code, North American specification and Australian/New Zealand standard. The evaluation results revealed that the codified design interaction curves led to conservative and scattered resistance predictions, mainly due to the conservative end points (i.e. the cross-section compression and bending resistances). Finally, a new design interaction curve, anchored to more accurate end points, was proposed and shown to result in a higher level of design accuracy and consistency than the codified design interaction curves.

Membrane residual stresses and compressive behaviour of laser-welded stainless steel T-sections

This paper reports experimental and numerical investigations into the membrane residual stresses and compressive behaviour of laser-welded stainless steel T-sections. An experimental programme was firstly conducted on eight T-sections and included tensile coupon tests, membrane residual stress measurements, initial local geometric imperfection measurements and sixteen stub column tests. On the basis of the measured data, a new membrane residual stress predictive model was proposed for laser-welded stainless steel T-sections. Following the experimental programme, a numerical modelling programme was performed, with finite element models developed and validated against the test results and then employed to perform parametric studies to generate additional numerical data over a wide range of cross-section dimensions. The obtained test and numerical data were used to evaluate the relevant local buckling design rules specified in the European code and American specification. The evaluation results revealed that (i) the codified slenderness limits were generally accurate when used for cross-section classification of laser-welded stainless steel T-sections in compression and (ii) both design codes resulted in slightly conservative and scattered cross-section compression resistance predictions.

Flexural buckling behaviour and residual resistances of hot-rolled stainless steel channel section columns after exposure to elevated temperatures

This paper presents experimental and numerical studies on the flexural buckling behaviour and residual resistances of hot-rolled stainless steel channel section columns after exposure to elevated temperatures ranging from 30 ℃ to 1000 ℃. An experimental programme, including heating, soaking and cooling of specimens as well as post-fire initial geometric imperfection measurements and fourteen pin-ended column tests, was firstly performed. The test procedures and results, including failure loads, load–deformation curves and failure modes, were reported in detail. Both ‘C’-shaped flexural buckling (with failure specimens buckling towards webs) and ‘reverse C’-shaped flexural buckling (with failure specimens buckling towards flange tips) were observed upon testing. The experimental programme was followed by a numerical modelling programme, where finite element models were developed and validated against the test results and used to conduct parametric studies to generate additional numerical data over a wide range of cross-section dimensions and member effective lengths. Due to the absence of design standards for stainless steel structures after exposure to elevated temperatures, the relevant ambient temperature buckling curves, as specified in the European code and American specification, were evaluated, using post-fire material properties, for their applicability to hot-rolled stainless steel channel section columns after exposure to elevated temperatures. The evaluation results revealed that the codified ambient temperature buckling curves in combination with post-fire material properties resulted in accurate and consistent post-fire residual resistance predictions for hot-rolled stainless steel channel section columns with ‘C’-shaped flexural buckling, but marginally conservative post-fire residual resistance predictions for their counterparts with ‘reverse C’-shaped flexural buckling.

Trigonometric projection statistics histograms for 3D local feature representation and shape description

Feature representation as a significant approach to three-dimensional (3D) shape description has been widely employed in computer vision. However, most existing methods are suffering from the emerging challenges for descriptiveness, robustness and efficiency. This paper presents a novel feature descriptor named trigonometric projection statistics histograms (TPSH). By constructing the repeatable local reference frame based on a multi-attribute weighting strategy, TPSH can address many prevailing nuisances such as noise, occlusion and varying resolution. The trigonometric projection mechanism is originally proposed for TPSH generation, which combines two perspective views to encode both spatial distribution and geometrical measurements from local shape into statistics histograms. The experimental evaluation on public datasets proves that TPSH outperforms state-of-the-art methods in descriptiveness and robustness while maintaining storage compactness and computational efficiency. It is demonstrated that TPSH can not only be suited for 3D object recognition and shape registration, but also generalized across various acquisition devices, data modalities and application scenarios.

P11: Mechanical Properties of the Common Bile Duct: Insights into Benign Biliary Structure Pathophysiology

Benign biliary strictures (BBS) that develop in the common bile duct (CBD) are often a result of postoperative or inflammatory processes. For instance, one-third of patients who undergo procedures such as cholecystectomy or liver transplants can develop surgery-related BBS. Current treatments for BBS are plagued by difficulties, complications, and failures, which result in high costs and risks associated with reinterventions. The failures may be due to a lack of knowledge about the structure of the CBD and the use of devices that are not designed for this specific application. This study aims to determine the mechanical properties of the CBD to better understand the pathophysiology of BBS, calibrate computational models, and the future evaluation of new treatment methods. Geometrical measurements and evaluations of the bile ducts (CBD, sphincter of Oddi, cystic, and common hepatic ducts) and the gallbladder were carried out on 31 adult pigs obtained from a local slaughterhouse. Pressurized diameter measurements were recorded at healthy and pathological pressures, and burst tests were performed on CBD sections (n=3). Longitudinal (lon, n=16) and circumferential (circ, n=25) tensile strength tests were performed on CBD sections at a rate of 50 mm/min until rupture, yielding the modulus of elasticity (E), ultimate strength, and fracture strengths. A creep test was performed in a bath at -4°C, with a weight of 3 g applied for 28 days. The test involved a 90° turn at day 14, with deformation monitored for 7 days without load (n=3). A high degree of variability was reported in bile duct size in terms of length (84.1 ± 17.5 mm) and relaxed diameter (6.2 ± 1.9 mm). The modulus of elasticity associated with elastin (0.111 ± 0.111 MPa) and collagen (4.744 ± 2.193 MPa) exceeded the circumferential values (0.019 ± 0.017 MPa and 2.850 ± 1.585 MPa, respectively). Lower results for the modulus of elasticity and higher dilation after the creep tests were observed in the proximal zone of the CBD near the duodenum (day 14: 41%, day 28: 43%, day 35: 67%), indicating lower stiffness. Additionally, all regions of the CBD retained most of their deformation even after 7 days in the absence of load. The data reported in this study provides valuable information on how the technique and treatment times can be improved in cases of BBS.

Improved flux-surface parameterization through constrained nonlinear optimization

Parameterization of magnetic flux-surfaces is often used for magnetohydrodynamic stability analysis and microturbulence modeling in tokamaks. Shape parameters for such local parameterization of a (numerical) equilibrium are traditionally computed analytically using geometrically derived quantities. However, often the shape is approximated by the average of values for different sections of the flux-surface contour or a truncated series, which does not guarantee an optimal fit. Here, instead nonlinear least squares optimization is used to compute these parameters, with a weighted sum of squared error cost function that is robust to outliers. This method results in a lower total absolute error for both the parameterization of the flux-surface contour and the poloidal magnetic field density than current methods for several parameterizations based on the well-known “Miller geometry.” Furthermore, rapid convergence of shape parameters is achieved, no approximate geometric measurements of the contour are needed, and the method is applicable to any analytical shape parameterization. Validation with local, linear gyrokinetic simulations using these optimized shape parameters showed reduced root mean square errors in both the growth rate and frequency spectra when compared with simulations based on numerical equilibria. In particular, the popular Turnbull–Miller parameterization benefits from this approach, extending its usability closer toward the last-closed flux-surface for cases with minor up-down asymmetry.

Determination of Geometrical Deviations of Large-Size Crankshafts with Limited Detection Possibilities Resulting from the Assumed Measuring Conditions

This article deals with the geometrical deviation measurements of crankshafts of large marine engines fuelled with conventional or alternative fuels, taking into account the problem of their deformability. Since the detectability of geometrical deviations of a crankshaft supported by prisms depends largely on the support conditions assumed and the parameters of the method, the study was carried out for two cases of crankshaft support. The first case concerned measurements of the main journals of a crankshaft seated on a set of supports pre-positioned at an equal height. In contrast, the second case involved measurements of the main journals of a crankshaft seated on supports pre-positioned at various heights. In particular, the research focused on evaluating the effect of sensor location angle on the results of measurements of deviations and contour profiles of the crankshaft main journal system. The results of the research are the developed procedures, the application of which in practical measurements under workshop conditions, where there is no access to coordinate measuring machines, enables correct interpretation of the measurement results and evaluation of the geometrical state of the measured crankshaft.

A Calibration Method for Large-Footprint Full-Waveform Airborne Laser Altimeter without a Calibration Field

The geometrical measurement precision of laser spots is affected by the deviation between the parameters of the laser altimeter and the laboratory measurement results, and the inversion accuracy of surface object height is also limited. The measurement parameters and the load state can be obtained by calibration of the laser altimeter system. Usually, ground detectors are deployed to calibrate the measurement parameters of the laser altimeter, including the divergence angle and the energy distribution of the laser beam. A calibration method for a laser footprint spot without a calibration field was proposed in this paper, focused on the airborne large-footprint laser altimeter system. The geometric parameters of the laser spot were calibrated through the laser echo waveforms of a specific terrain. The experimental results show that geometric calibration of the large-footprint laser altimeter can be achieved in the area of the step surface. The divergence angle of the laser beams obtained from the six experimental areas is 4.604 ± 0.359 mRad, and the consistency of the energy distribution from each laser spot reaches 92.67%. A new method of on-orbit calibration and verification is provided for the satellite laser altimeter system.

Near-zero beam drift laser tracking and measurement system with two-stage compression structures.

This paper introduces a scheme of near-zero beam drift tracking technology with two-stage compression structures for the coordinate accuracy measurement of a laser tracker. The Galileo telescope system, with a magnification of 21.43, is designed to compress the beam drift in a dual-frequency interferometer. The azimuth and pitch of the beam drift are compressed to 2.41in. and 2.92in., and the compression rates are 95.0% and 91.9%, respectively. The improved four degrees of freedom position-sensitive detector system is used to further compress the beam drift. The peak-to-peak value of the beam drift is 0.9in. in the azimuth direction and 2.1in. in the pitch direction. The standard deviation of azimuth is within 0.15in, and the pitch is within 0.43in. The coordinate accuracy of the laser tracker can be improved 6.85 parts per million by simulation. The developed two-stage compression near-zero beam drift system can be used in the laser tracker to realize large-scale precision instrument geometric measurement.

Geometric Error Parameterization of a CMM via Calibrated Hole Plate Archived Utilizing DCC Formatting

This study implemented the measurement results and administrative information obtained from the hole plate into the Digital Calibration Certificate (DCC). The DCC comprises three parts: Norms and Standards, Hierarchical Structure, and XML as Exchange Format. DCCs play a significant role in the field of metrology and statistics by ensuring data interoperability, correctness, and traceability during the conversion and transmission process. The hole plate is a length standard used for two-dimensional geometric error measurements. We evaluated the accuracy of the high-precision coordinate measuring machine (CMM) in measuring a hole plate and compared the measurement error results obtained from the hole plate with those of the laser interferometer, autocollimator, and angle square. The results show that the maximum difference in linear error is −0.30 μm, the maximum difference in angle error is −0.78″, and the maximum difference in squareness error is 4.54″. The XML is designed for machine-readability and is modeled and edited using the XMLSpy 2022 software, which is based on information published by PTB. The administrative management and measurement results tasks are presented in PDF format, which is designed for human-readability and ease of use. Overall, we implemented the measurement results and information obtained from the hole plate into the DCC.

A graph autoencoder network to measure the geometric similarity of drainage networks in scaling transformation

ABSTRACT Similarity measurement has been a prevailing research topic in geographic information science. Geometric similarity measurement in scaling transformation (GSM_ST) is critical to ensure spatial data quality while balancing detailed information with distinctive features. However, GSM_ST is an uncertain problem due to subjective spatial cognition, global and local concerns, and geometric complexity. Traditional rule-based methods considering multiple consistent conditions require subjective adjustments to characteristics and weights, leading to poor robustness in addressing GSM_ST. This study proposes an unsupervised representation learning framework for automated GSM_ST, using a Graph Autoencoder Network (GAE) and drainage networks as an example. The framework involves constructing a drainage graph, designing the GAE architecture for GSM_ST, and using Cosine similarity to measure similarity based on the GAE-derived drainage embeddings in different scales. We perform extensive experiments and compare methods across 71 drainage networks during five scaling transformations. The results show that the proposed GAE method outperforms other methods with a satisfaction ratio of around 88% and has strong robustness. Moreover, our proposed method also can be applied to other scenarios, such as measuring similarity between geographical entities at different times and data from different datasets.

Magnitude of formative flows in stream potholes

Although it is generally recognized that geomorphic work is tied to bedrock channel reshaping, the importance of low vs. high flow stages that cause the most geomorphic impact remains unclear. The objective of the research is to study the concept of “formative flow” in bedrock channels and determine, through morphological studies, if those flows have any impact on sculpted features such as potholes and how this relationship relates to various inputs such as flow stages (magnitude and frequency), shear stress, and sediment size. Here, we studied the distribution of the main pothole typologies and tried to understand why potholes are found along bedrock river channels. Specifically, we examined stream potholes from three locations along the Spanish Central System: Alberche, Tietar, and Manzanares rivers. We conducted the research by taking precise geometric measurements, classifying potholes, analyzing flow magnitude and frequency, and using a two-dimensional (2D) hydrodynamic model to assess key variables in Manzanares river. This research demonstrated that bankfull depths completely cover all pothole typologies in all the analyzed sites but are not sufficient to achieve its formative flow depth (FFD). Using a detailed 2D hydrodynamic model in Manzanares river, we discovered that dimensions of cylindrical potholes are closely related to bankfull discharge and that this depth is connected to FFD. Other potholes, such as erosive-compound and erosive-lateral, are historical remnants, and their shapes are not related to any particular FFD and are likely associated with rare events and catastrophic breaks. A collection of laterals that exhibit FFD near bankfull flows appear to represent a part of the recent evolution of a knickpoint. To summarize, it can be inferred from the findings that the utility of morphological analysis in conjunction with the 2D hydrodynamic model is to examine the fraction of erosional/active features to determine the degree of senescence and/or change in natural conditions in a river reach.

Genetic basis of ecologically relevant body shape variation among four genera of cichlid fishes.

Divergence in body shape is one of the most widespread and repeated patterns of morphological variation in fishes and is associated with habitat specification and swimming mechanics. Such ecological diversification is the first stage of the explosive adaptive radiation of cichlid fishes in the East African Rift Lakes. We use two hybrid crosses of cichlids (Metriaclima sp. × Aulonocara sp. and Labidochromis sp. × Labeotropheus sp., >975 animals total) to determine the genetic basis of body shape diversification that is similar to benthic-pelagic divergence across fishes. Using a series of both linear and geometric shape measurements, we identified 34 quantitative trait loci (QTL) that underlie various aspects of body shape variation. These QTL are spread throughout the genome, each explaining 3.2-8.6% of phenotypic variation, and are largely modular. Further, QTL are distinct both between these two crosses of Lake Malawi cichlids and compared to previously identified QTL for body shape in fishes such as sticklebacks. We find that body shape is controlled by many genes of small effect. In all, we find that convergent body shape phenotypes commonly observed across fish clades are most likely due to distinct genetic and molecular mechanisms.

Testing, FE modelling and design of pin-ended stainless steel equal-leg angle section columns and beam–columns

The behaviour and design of pin-ended stainless steel equal-leg angle section members under compression and compression plus minor-axis bending are investigated herein. The studied members are cylindrically pinned about the minor axis. An experimental investigation, including material testing, initial geometric imperfection measurements and physical tests on hot-rolled stainless steel equal-leg angle section members is first presented. Numerical models are developed and validated against the new experimental data. A numerical parametric study is then presented considering both hot-rolled and cold-formed stainless steel angle section columns alongside beam–columns with a wide range of slenderness values. Finally, new design proposals for pin-ended stainless steel equal-leg angle section members under compression and combined compression and minor-axis bending are developed and verified against the results of existing physical experiments, as well as the newly-generated test and numerical results. The proposed design rules are shown to offer substantially more accurate and consistent resistance predictions compared to existing codified design rules. The reliability of the new design provisions, with a recommended partial safety factor γM1=1.1, is verified following the EN 1990 procedure.

Cross-section behaviour and design of press-braked ferritic stainless steel channel sections under combined compression and major-axis bending moment

This paper presents experimental and numerical investigations into the cross-section behaviour and resistance of press-braked ferritic stainless steel channel sections under combined compression and major-axis bending moment. An experimental programme, including initial local geometric imperfection measurements and ten major-axis eccentric compression tests, was firstly conducted, with the test setup, procedures and results reported in detail. This was followed by a numerical modelling programme, where finite element models were developed and validated against the major-axis eccentric compression test results and then adopted to conduct parametric studies to expand the test data pool over a wider range of cross-section dimensions and loading combinations. Based on the obtained test and numerical data, the design interaction curves for press-braked ferritic stainless steel channel sections under combined compression and major-axis bending moment, as given in the American specification and European code, were evaluated. The evaluation results revealed that the American specification resulted in a good level of design accuracy, while the European code led to conservative resistance predictions, due to the conservative bending end point and inefficient linear shape of the design interaction curve. New design interaction curves were also developed and shown to offer more accurate and consistent resistance predictions for press-braked ferritic stainless steel channel sections under combined compression and major-axis bending moment than the codified design interaction curves.

A new method for determining loess particle size distribution based on ‘core + clothes’ structure

AbstractThe particle size distribution (PSD) of loess particles and agglomerates is the key factor determining the microstructure of loess. The PSD largely determines many physical and mechanical properties such as mechanical strength, deformation characteristics and permeability of loess. In this paper, we combined image processing, geometric measurements and statistical methods to quantitatively characterize the scanning electron microscopy (SEM) images of loess. A new method based on the ‘core + clothes’ structure is proposed to determine the PSD. The developed Gaussian mixture model is applicable to describe the overall distribution of the image pixel density. Determining pixel density distribution and particle boundary allows for the measurement of various geometric parameters. The comparison analyses suggest that the sieve‐hydrometer method has a well‐developed test procedure; however, the measured particle size is limited to 0.075 mm. The laser diffraction method is simple and fast, yet only weak agglomerates can be dispersed, and very fine particles are influenced by size data conversion theory and light source parameters. X‐ray microtomography has the advantage of a non‐destructive sample preparation and intuitive process. However, the results are greatly affected by the parameter settings and segmentation algorithm, and the segmentation effect is poor for particles with a size smaller than 12 μm. The new image processing technique developed in this study improves the limitation of the measurement results via changes in the loess state (water content, stress level). Moreover, different PSDs can be determined according to the variation of functional units. This work is of great significance for the study of numerous properties related to the loess state.

Research on the Estimation Method of Target Motion Parameters Based on Ternary Array

The ternary array passive positioning technique performs the estimation of target distance and bearing by measuring the time delay difference between array elements. The estimates are limited by the geometric model and time delay measurement errors, and the positioning accuracy and reliability are poor. In this paper, we propose an orientation matching-based motion target localization model. By introducing the target motion model, and establish a matching objective function for the time delay difference obtained by calculating the predefined target motion trajectory and the actual received data of the ternary array separately. The matching objective function is optimally solved by using Burg algorithm in the AR spectrum estimation method, and a highly accurate and reliable target parameter estimation can be obtained in a short time. The results of computer simulation experiments verify the effectiveness of the method.

Udo Krüger Charts TechnoTeam's Journey

Udo Krüger Charts TechnoTeam's Journey